Guide: Determining the Size of Your Wheels
Last month we discussed whether or not mismatched wheels and tires are safe on the road. It was determined that mismatched wheels can be a temporary solution, so long as the front two wheels match and the two rear wheels match.
However, the best and safest option when you’re just replacing one or two wheels, is to replace with the same OEM wheels currently on your vehicle. This guide is for drivers who need to replace a wheel for the first time.
Understanding the Numbers on Your Car Tire
Every vehicle has a standard nomenclature for reference with all the information you should need. Printed on the side of each auto tire is a series of numbers that looks something like this:
The first letter is usually a ‘P,’ which stands for ‘Passenger’ Vehicle. For light trucks, it will start with an ‘LT.’
The three digit number immediately following, in our example ‘195’, is the tire width, measured in millimeters from sidewall to sidewall.
After the slash mark, the two digit number is the tire ‘aspect ratio,’ which is expressed as a percentage. In our example, the tire aspect ratio is ‘75,’ which tells us that the tire height is 75% of the tire width.
Another letter follows the aspect ratio, which nowadays is almost always an ‘R,’ for Radial. This bit of information details the internal construction of your tire and is otherwise not very useful for our purposes.
Now, the last two digit number is very important. This is the diameter of the wheel itself, measured in inches. In our example, the wheel diameter is 15 inches. When replacing the rims on your car, this is the number you need to know for size.
Take note of this number next time you’re near your car. A quick Google search for ‘(year) (car make) (car model) rim size’ will tell you what the standard OEM wheels were for your vehicle.
When replacing a wheel or wheel set, it’s necessary to have an understanding of this concatenated nomenclature. You can use the popular Blackburn WheelFinder to find the correct replacement wheel in just minutes.
If you are deciding between steel and alloy to replace a full set of wheels, here is a handy article on the pros and cons of alloy vs. steel wheels.